Hydraulic Transport Refrigeration System

ABSTRACT

A transport refrigeration system includes an engine, a hydraulic pump driven by the engine, a supply line coupled to an output of the pump, a supply control valve coupled to the supply line and a refrigerant compressor coupled to the supply control valve through a compressor supply line. The refrigerant compressor speed is responsive to fluid flow in the compressor supply line.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate generally to transport refrigeration, and more particularly to a hydraulic transport refrigeration system.

Existing transport refrigeration systems use an engine (e.g., gas or diesel engine) to drive refrigeration system components (e.g., compressor, fans). In order to improve efficiency and reduce emissions, hybrid systems have been proposed to power the transport refrigeration system. One hybrid system, described in U.S. Patent Application Publication 20110000244 and assigned to Carrier Corporation, uses an electrical hybrid power supply. While existing designs are well suited for their intended purposes, improvements in hybrid transport refrigeration systems would be well received in the art.

BRIEF DESCRIPTION OF THE INVENTION

According to an exemplary embodiment of the present invention, a transport refrigeration system includes an engine; a hydraulic pump driven by the engine; a supply line coupled to an output of the pump; a supply control valve coupled to the supply line; and a refrigerant compressor coupled to the supply control valve through a compressor supply line, the refrigerant compressor speed being responsive to fluid flow in the compressor supply line.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 depicts a hydraulic transport refrigeration system in exemplary embodiments;

FIG. 2 depicts mounting of the transport refrigeration system of FIG. 1 to a trailer; and

FIG. 3 depicts an exemplary semi-hermetic compressor for use in the transport refrigeration system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a hydraulic powered transport refrigeration system 100 in exemplary embodiments. The transport refrigeration system 100 includes an engine 102 that drives a pump 104. Pump 104 provides hydraulic fluid to components of the transport refrigeration system 100. Engine 102 may be a standalone engine (gas or diesel) or may be the engine of the vehicle directly driving pump 104 through, for example, a flywheel. Alternatively, engine 102 may be a combination of a standalone engine and the engine of the vehicle operating in conjunction. This allows the run time of the standalone engine to be reduced, particularly during periods when the vehicle engine has extra capacity (e.g., vehicle idling).

A supply line 106 from an output of pump 104 provides fluid to supply control valve 108. Supply control valve 108 is fluidly coupled to a high-pressure accumulator 110, motor 112 and compressor 114. Compressor 114 is coupled to supply control valve 108 by a compressor supply line 115. It is understood that multiple supply control valves may be used, each coupled to an individual system component. Supply line 106 may be coupled to a manifold, with several supply control valves independently controlled by controller 116 as described herein.

Motor 112 drives a fan shaft 113 for turning a fan (e.g., evaporator fan, condenser fan) in the transport refrigeration system 100. Only one motor 112 is shown, but it is understood that multiple motors 112 may be used, each for a respective system component. Further, a single motor 112 may be coupled to multiple fans, pumps, etc.

A controller 116 receives a number of input signals 118 indicative of the operational status of the transport refrigeration system 100 and adjusts supply control valve 108 accordingly. Input signals 118 may represent parameters such a pressure, temperature, speed, etc. and are generated by sensors within transport refrigeration system 100. Under periods of light load on the transport refrigeration system, controller 116 diverts fluid to high-pressure accumulator 110 to store fluid in a pressurized state. When demand on the transport refrigeration system increases, controller 116 can direct fluid from the high pressure accumulator 110 to motor 112 and compressor 114. This arrangement allows the compressor 114 speed to be independent of engine 102 speed. Controller 116 may be implemented using a general-purpose processor executing software instructions to perform the steps described herein. Alternatively, controller 116 may be implemented in hardware, or with a combination of hardware and software.

Motor 112 and compressor 114 are fluidly coupled to a return control valve 120. Compressor 114 is coupled to return control valve 120 by a compressor return line 117. Return control valve 120 is coupled to an input of pump 104 via a return line 122 and is coupled to a low-pressure reservoir 124. Controller 116 controls the return control valve 120 in response to input signals 118 indicative of the operational status of the transport refrigeration system 100. For example, under periods of light load on the transport refrigeration system 100, return control valve 120 diverts excess fluid to reservoir 124. It is understood that multiple return control valves may be used, each coupled to an individual system component.

In the embodiment of FIG. 1, compressor 114 is a hermetic, hydraulically driven compressor. Fluid from the supply control valve 108 drives the compressor and is returned to pump 104 through return control valve 120. In alternate designs, the pump 104 and compressor 114 are encased together in a common housing preventing loss of refrigerant that is typical in open drive systems.

FIG. 2 illustrates exemplary mounting of the transport refrigeration system 100 to a trailer 150. As shown in FIG. 2, the high-pressure accumulator 110 and the low pressure reservoir 124 are mounted to the underside of the trailer 150. The remaining components of transport refrigeration system 100 may be mounted on a front face of trailer 150. The evaporator coil and evaporator fan (not show) may be positioned within trailer 150 as known in the art.

The embodiment of FIG. 1 provides a hydraulic hybrid transport refrigeration system 100 that improves efficiency. The high-pressure accumulator 110 stores excess fluid pressure to drive system components. By storing the fluid pressure, engine 102 need not run, at least part of the time, when under light loads. Engine power may also be supplemented during high load transients such as during starts of the compressor 114, allowing a smaller engine 102 to be used. Additional savings would result as the engine could be shut down under light load and the system ran off the accumulated energy via the accumulator 110. Other savings may include reduced total cost of ownership of the unit, reduced noise, reduced weight, improved reliability of the compressor, design latitude for fan designs, removal of belts typically used for fans, design latitude for engine power/speed as well as component driven speed. In addition, variable pitch pumps and motors can be used as well as simple regulators to control speeds of fan, compressor, and other devices.

FIG. 3 depicts an exemplary semi-hermetic compressor 200 for use in the transport refrigeration system. Compressor 200 includes a casing 202 housing elements of the compressor. A hydraulic compressor motor 204 is positioned in a chamber 206 of casing 202. Compressor supply line 115 is coupled to a compressor control valve 210. Compressor control valve 210 is controlled by controller 116 and controls the flow of fluid to compressor motor 204. Compressor control valve 210 may divert some fluid to compressor return line 117 via a bypass line 212. This allows the compressor speed to be controlled independently of engine speed. Fluid returned from the compressor motor 204 is filtered at filter 214 and then provided to compressor return line 117.

Refrigerant from suction port 216 is drawn into compression mechanism 220 of compressor 200, where the refrigerant is compressed and output through discharge port 222. The compressor of FIG. 3 is a reciprocating compressor, but other types of compressors may be used. An oil separator 224 may be positioned in fluid communication with the discharge port 222. The oil separator 224 is fluidly coupled to the compressor return line 117 to return oil to the return control valve 120.

Referring to FIG. 3, the shaft of the motor 204 is not exposed to atmosphere, but rather to compressor internal pressure. This provides for better compressor vacuum and better performance. Also, any leaks in the seal around the shaft of motor 204 do not result in a loss of refrigerant. The fluid in the compressor supply line 115 that drives compressor motor 204 may be the same oil used to lubricate the compressor. If motor 204 leaks fluid, the leaked fluid can re-enter the compression mechanism 220 through an oil check valve 226 positioned between chamber 206 and compression mechanism 220.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

1. A transport refrigeration system comprising: an engine; a hydraulic pump driven by the engine; a supply line coupled to an output of the pump; a supply control valve coupled to the supply line; and a refrigerant compressor coupled to the supply control valve through a compressor supply line, the refrigerant compressor speed being responsive to fluid flow in the compressor supply line.
 2. The transport refrigeration system of claim 1 further comprising: a high pressure accumulator coupled to the supply control valve.
 3. The transport refrigeration system of claim 2 wherein: the high pressure accumulator is coupled to the compressor through the supply control valve when the engine is at low speed.
 4. The transport refrigeration system of claim 2 wherein: the high pressure accumulator is coupled to the compressor through the supply control valve upon start of the compressor.
 5. The transport refrigeration system of claim 1 further comprising: a return line coupled to an input of the pump; a return control valve coupled to the return line; and a reservoir coupled to the return control valve.
 6. The transport refrigeration system of claim 1 further comprising: a hydraulic motor coupled to the supply control valve.
 7. The transport refrigeration system of claim 6 wherein: the hydraulic motor drives a fan.
 8. The transport refrigeration system of claim 1 further comprising: a controller for controlling the supply control valve in response to input signals indicative of the operational status of the transport refrigeration system.
 9. The transport refrigeration system of claim 1 wherein: the compressor is a hermetic compressor.
 10. The transport refrigeration system of claim 1 wherein: the compressor is a semi-hermetic compressor.
 11. The transport refrigeration system of claim 10 wherein: the compressor includes a hydraulic motor coupled to the compressor supply line.
 12. The transport refrigeration system of claim 11 wherein: the compressor includes a casing, the casing having a chamber containing the hydraulic motor, the casing housing a compressor mechanism.
 13. The transport refrigeration system of claim 12 further comprising: an oil check valve providing a passage for oil from the chamber to the compressor mechanism.
 14. The transport refrigeration system of claim 11 further comprising: a compressor control valve coupled to the compressor supply line.
 15. The transport refrigeration system of claim 14 wherein: the compressor control valve is coupled to a compressor return line via a bypass line.
 16. The transport refrigeration system of claim 1 wherein: the fluid in the compressor supply line is oil suitable for lubricating the compressor.
 17. The transport refrigeration system of claim 1 wherein: the engine is a vehicle engine. 